register Webhook shrows an exception when processing returned data

[wwalex]

Description
When registereing a Webhook, the returned data is passed to a new instance of Webhook class, which uses
function applyV1() to add the json data to the object.
This results in the following error:
Fatal error: Uncaught TypeError: Argument 1 passed to Trunkrs\SDK\Util\JsonDateTime::from() must be of the type string, null given

Looking at the returned data, it has the field
'created_at' => '.....',
While the code has
$webhook->createdAt = JsonDateTime::from($json->createdAt);

How to reproduce
$webhook = new \Trunkrs\SDK\Webhook();
$webhook->callbackUrl = "https://domain.name/";
$webhook->sessionHeaderName = 'XXXX';
$webhook->sessionToken = "yyyy";

$result = \Trunkrs\SDK\Webhook::register($webhook);

Possible Solution
Either have the API return createdAt or change the code to
$webhook->createdAt = JsonDateTime::from($json->created_at);

Additional context
Have only tested on staging, not sure if it also happens on live